Method and Apparatus for Advancing a Probe

ABSTRACT

Some embodiments relate to an apparatus comprising an elongate flexible tube sized to be received within a tract and having a proximal end and a distal end; a drive mechanism coupled to the proximal end of the tube; and a liquid column extending from the proximal end to the distal end; wherein the drive mechanism is configured to cause movement of the liquid column within the tube to impart forward momentum to the tube and thereby promote advancement of at least the distal end of the tube within the tract when at least the distal end is received within a part of the tract.

TECHNICAL FIELD

Described embodiments relate to methods and apparatus for use inadvancing a probe. In particular, embodiments may be used for advancinga probe across a surface or within a tract, such as biological tract.

BACKGROUND

It can be difficult to explore tracts, tight spaces or areas not readilyaccessible to a person. This is particularly so where adequate controlof advancement of a probe can be problematic. For example, intestinaltracts are often relatively long and form a convoluted path, which isdifficult for a probe to traverse without the aid of some form of deviceassisting the advancement of the probe.

Tracts such as intestinal and vascular tracts may be beneficiallyexplored using a probe for medical purposes.

It is desired to address or ameliorate one or more shortcomings ordisadvantages associated with existing methods and/or apparatus foradvancing probes, or to at least provide a useful alternative thereto.

SUMMARY

Some embodiments relate to apparatus comprising:

-   -   an elongate flexible tube sized to be received within a tract        and having a proximal end and a distal end;    -   a drive mechanism coupled to the proximal end of the tube; and    -   a liquid column extending from the proximal end to the distal        end;    -   wherein the drive mechanism is configured to cause movement of        the liquid column within the tube to impart forward momentum to        the tube and thereby promote advancement of at least the distal        end of the tube within the tract when at least the distal end is        received within a part of the tract.

The liquid column may be part of a liquid volume enclosed by the tubeand drive mechanism. The tube may have periodic perturbations formed onan external surface of the tube along at least part of the distal end.The periodic perturbations may extend circumferentially around the tubeand may have a radial variance of a same order of magnitude as a radialthickness of a wall of the tube.

An external surface of the tube may be contoured to enhance resistanceto movement of the tube in a reverse direction. An internal surface ofthe tube may be contoured to enhance resistance to movement of thecolumn through the tube in the forward direction. The external andinternal surfaces of the tube (i.e. periodic perturbations) may beformed in a proximally swept fir tree pattern. Internal periodicperturbations may be formed along at least a section of the tube that isdistal of the proximal end.

A liquid of the liquid column may have a density of about the same as orgreater than the density of water, so that the liquid compressesminimally when the liquid column is acted upon by the drive mechanism.

The drive mechanism may be configured to impart a specific speed profileto a proximal end of the liquid column to enhance forward movement ofthe tube within the tract. The speed profile may comprise one or moreof:

-   -   a gradual acceleration portion at a first part of a forward        movement of the liquid column;    -   a sharp deceleration portion at a second part of the forward        movement of the liquid column following the first part of the        forward movement;    -   a sharp acceleration portion at a first part of a rearward        movement of the liquid column; and    -   a gradual deceleration portion at a second part of the rearward        movement of the liquid column following the first part of the        rearward movement.

The drive mechanism may comprise a piston and a drive member, such as ashaft, configured to cause repeated advancement and retraction of theliquid column within the tube. The drive mechanism may be configured tocause the piston to sharply decelerate toward the end of each stroke ofthe piston and/or to sharply accelerate away from the end of each strokeof the piston.

The apparatus may further comprise a flexible membrane within the tubeat the distal end for enclosing a distal end of the fluid column. Thedistal end of the tube may house a compressive fluid volume (e.g. air oranother low density inert gas) bounded by the tube, the flexiblemembrane and another membrane positioned distally of the flexiblemembrane. The other membrane may also be flexible, with both membranesbeing elastically deformable in response to advancement of the liquidcolumn.

An internal diameter of the tube may narrow in the distal direction.This narrowing may be stepped and/or gradual. This narrowing may assistin minimising loss of pressure in the liquid column towards the distalend while the drive mechanism moves the liquid column. The tube wall maybe reinforced by some form of reinforcing means to help the tube resistexpanding or collapsing in response to pressure differences created bythe action of the drive mechanism.

A probe may be located at the distal end of the tube. The probe mayhouse an imaging device for capturing images of an area in front of theprobe. A plurality of conduits may extend along the tube and be coupledto the probe, for example to send and/or receive signals to and/or fromthe probe. The conduits may be disposed within the tube along at leastpart of the tube. At least one of the conduits may extend in a spiralalong at least part of the tube. In some embodiments, a secondary lumenmay extend within a primary lumen defined by the tube and one or more ofthe conduits may extend within the secondary lumen along at least partof the tube. In some embodiments, one or more of the conduits may beembedded within the tube wall along at least part of a length of thetube.

The tract within which the tube is sized to extend may be a digestivetract or a vascular tract, for example. Alternatively, the tract may bea non-biological structure or area, such as a pipe, conduit, containeror other structure that may be difficult or dangerous for a person toaccess and/or inspect.

Further embodiments relate to a method of advancing a probe, the methodcomprising:

-   -   positioning a distal end of an elongate flexible tube at least        partly within a lower end of a tract, the tube being sized to be        received within the tract and having a liquid column extending        from a proximal end of the tube to the distal end, wherein the        probe is located at the distal end of the tube; and    -   operating a drive mechanism to cause advancement of the liquid        column within the tube to impart forward momentum to the tube        and thereby promote advancement of at least the distal end of        the tube within the tract.

The operating may comprise imparting a specific speed profile to aproximal end of the liquid column to enhance forward movement of thetube within the tract. The speed profile may comprise at least one of:

-   -   a gradual acceleration portion of a first part of a forward        movement of the liquid column;    -   a sharp deceleration portion of a second part of the forward        movement of the liquid column following the first part of the        forward movement;    -   a sharp acceleration portion of a first part of a rearward        movement of the liquid column; and    -   a gradual deceleration portion at of a second part of the        rearward movement of the liquid column following the first part        of the rearward movement.

The operating may comprise operating a piston and a drive shaft to causerepeated advancement and retraction of the liquid column within thetube. The operating may cause the piston to sharply decelerate towardthe end of each stroke of the piston (i.e. just prior to the point ofmaximum stroke). The operating may cause the piston to sharplyaccelerate away from the end of each stroke of the piston (i.e. justafter the point of maximum stroke).

The method may further comprise providing contours along the outside ofthe tube to resist movement of the tube in a reverse direction withinthe tract, and may comprise providing contours along the inside of thetube to resist movement of the liquid column through the tube in adistal direction.

The probe may comprise an imaging device, and the method may furthercomprise capturing images within the tract using the imaging device. Themethod may further comprise transmitting image data corresponding to thecaptured images to a system configured to process and display theimages. Conduits, including at least one electrical conduit, may extendalong the tube to perform at least one of sending and receiving signalsto and from the probe, and the transmitting may be performed using theat least one electrical conduit.

Some embodiments relate to an advancement method comprising inducingreciprocating movement of a liquid column extending within an elongatemember from one end of the member to an opposite end of the member toimpart forward movement of the member along a length of the elongatemember.

Some embodiments relate to apparatus comprising a probe positioned atone end of an elongate member and a drive mechanism at an opposite endof the elongate member, the elongate member housing a liquid columnextending from the one end to the opposite end, wherein the drivemechanism causes reciprocating movement of the liquid column within theelongate member to impart forward movement to the probe.

Some embodiments relate to a replaceable self-advancing tube assemblycomprising an elongate flexible tube, a liquid chamber disposed at aproximal end of the tube and a probe disposed at a distal end of thetube, the tube having a liquid column extending between the liquidchamber and the distal end.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described in detail below, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of a system for use in advancing aprobe within a tract;

FIG. 2 is a graph of an illustrative speed profile to be imparted to aliquid column;

FIG. 3 is a schematic representation of advancement apparatus to be usedto advance a probe;

FIG. 4A is a schematic side-sectional view of a proximal portion of atube forming part of the advancement apparatus of FIG. 3;

FIG. 4B is schematic side-sectional view of a distal part of theadvancement apparatus of FIG. 3;

FIG. 5A is a schematic representation illustrative of a flexiblemembrane positioned toward a distal end of the advancement apparatus,with the membrane shown in a relaxed position;

FIG. 5B is a schematic diagram illustrative of the membrane of FIG. 5A,with the membrane shown in a deformed position;

FIG. 6 is a schematic diagram of a system for advancing a probeaccording to some embodiments;

FIG. 7A is a partial side sectional view of a tube according to someembodiments;

FIG. 7B is a cross-sectional view of the tube of FIG. 7A, taken alongline 7-7;

FIG. 8A is a side view of a tube according to some embodiments;

FIG. 8B is a cross-sectional view of the tube of FIG. 8A, taken alongline 8-8;

FIG. 9A is a side view of a tube according to some embodiments;

FIG. 9B is a cross-sectional view of the tube of FIG. 9A, taken alongline 9-9;

FIG. 10A is a side view of a tube according to some embodiments;

FIG. 10B is a cross-sectional view of the tube of FIG. 10A, taken alongline 10-10;

FIG. 11A is a side view of a tube according to some embodiments;

FIG. 11B is a cross-sectional view of the tube of FIG. 11A, taken alongline 11-11;

FIG. 12A is a partial side sectional view of a tube according to someembodiments;

FIG. 12B is a cross-sectional view of the tube of FIG. 12A, taken alongline 12-12;

FIG. 13A is a partial side sectional view of a tube according to someembodiments;

FIG. 13B is a cross-sectional view of the tube of FIG. 13A, taken alongline 13-13;

FIG. 13C is an alternative cross-sectional view of the tube of FIG. 13A,taken along line 13-13;

FIG. 14A is a partial side sectional view of a tube according to someembodiments;

FIG. 14B is a cross-sectional view of the tube of FIG. 14A, taken alongline 14-14;

FIG. 15A is a partial side sectional view of a tube according to someembodiments;

FIG. 15B is a cross-sectional view of the tube of FIG. 15A, taken alongline 15-15;

FIGS. 16A and 16B are schematic representations of a piston movingwithin a chamber according to some embodiments of a drive mechanism;

FIGS. 17A and 17B are schematic representations of a piston movingwithin a chamber according to some embodiments of a drive mechanism;

FIG. 18 is a schematic representation of a piston acting on a flexiblemembrane of a fluid chamber according to some embodiments of a drivemechanism;

FIG. 19 is a schematic representation of a piston of circularcross-section that is eccentrically rotatable to displace a membrane ofa fluid chamber according to some embodiments of a drive mechanism;

FIG. 20 is a schematic representation of a fluid chamber having a pistonmovable within the chamber under the control of electromagneticelements, according to some embodiments of a drive mechanism;

FIG. 21 is a schematic representation of a distal biasing chamberaccording to some embodiments;

FIG. 22 is a schematic representation of a distal biasing chamberaccording to some embodiments;

FIG. 23 is a schematic representation of a distal biasing chamberaccording to some embodiments;

FIG. 24 is a schematic representation of a distal biasing chamberaccording to some embodiments;

FIG. 25 is a schematic representation of a distal biasing chamberaccording to some embodiments, shown in an uncompressed state;

FIG. 26 is a schematic representation of the distal biasing chamber ofFIG. 25 in a compressed state;

FIG. 27 is a schematic representation of a distal biasing chamberaccording to some embodiments, shown in an uncompressed state;

FIG. 28 is a schematic representation of the distal biasing chamber ofFIG. 27 in a compressed state;

FIG. 29 is a schematic representation of a distal biasing chamberaccording to some embodiments;

FIG. 30 is a schematic representation of a distal biasing chamberaccording to some embodiments;

FIG. 31 is a schematic representation of a distal biasing chamberaccording to some embodiments;

FIG. 32 is a schematic representation of a distal biasing chamberaccording to some embodiments, shown in an uncompressed state;

FIG. 33 is a schematic representation of the distal biasing chamber ofFIG. 32 in a compressed state;

FIG. 34 is a schematic representation of a distal biasing chamberaccording to some embodiments, shown in an uncompressed state;

FIG. 35 is a schematic representation of the distal biasing chamber ofFIG. 34 in a compressed state;

FIG. 36 is a schematic representation of a distal biasing chamberaccording to some embodiments;

FIG. 37A is a partial side-sectional view of part of a tube according tosome embodiments, showing periodic perturbations along an externalsurface of the tube;

FIG. 37B is a partial side-sectional view of part of a tube according tosome embodiments, showing periodic perturbations along an externalsurface of the tube;

FIG. 38A is a partial side-sectional view of part of a tube according tosome embodiments, showing periodic perturbations along an externalsurface of the tube;

FIG. 38B is a partial side-sectional view of part of a tube according tosome embodiments, showing periodic perturbations along an externalsurface of the tube;

FIG. 39A is a partial side-sectional view of part of a tube according tosome embodiments, showing periodic perturbations along an externalsurface of the tube;

FIG. 39B is a partial side-sectional view of part of a tube according tosome embodiments, showing periodic perturbations along an externalsurface of the tube;

FIG. 40A is a partial side-sectional view of a tube according to someembodiments, showing periodic perturbations along an internal surface ofthe tube;

FIG. 40B is a partial side-sectional view of a tube according to someembodiments, showing periodic perturbations along an internal surface ofthe tube;

FIG. 41A is a partial side-sectional view of a tube according to someembodiments, showing periodic perturbations along an internal surface ofthe tube;

FIG. 41B is a partial side-sectional view of a tube according to someembodiments, showing periodic perturbations along an internal surface ofthe tube;

FIG. 42A is a partial side-sectional view of a tube according to someembodiments, showing periodic perturbations along an internal surface ofthe tube;

FIG. 42B is a partial side-sectional view of a tube according to someembodiments, showing periodic perturbations along an internal surface ofthe tube;

FIG. 43A is a partial side-sectional view of a part of a tube accordingto some embodiments, showing periodic perturbations along both theinternal and external surfaces of the tube;

FIG. 43B is a partial side-sectional view of a part of a tube accordingto some embodiments, showing periodic perturbations along both theinternal and external surfaces of the tube; and

FIG. 44 is a partial side-sectional view of a part of a tube accordingto some embodiments, showing periodic perturbations formed alonginternal and external surfaces of a tube in sections that are spacedalong the tube.

DETAILED DESCRIPTION

The described embodiments relate generally to methods and apparatus foruse in advancing a probe. As different kinds of probes may be used withthe described embodiments, this description will focus primarily onapparatus and methods for advancing the probe within a tract, passage orarea. The described methods and apparatus employ an elongate flexibletube defining a lumen and sized to be received within the tract, passageor area and having a proximal end and a distal end. A drive mechanism iscoupled to the proximal end of the tube and a liquid column extendswithin the lumen from the proximal end to the distal end of the tube.The drive mechanism is configured to cause movement of the liquid columnwithin the tube to impart forward movement to the tube, which promotesadvancement of at least the distal end of the tube within the tract,passage or area when at least the distal end is supported by a part ofthe tract, passage or area.

Generally, the movement of the liquid column within the lumen impartsmomentum to the inner wall of the tube along most of the length of thetube by friction and/or turbulence. For example, for a tube of about 3metres in length, the movement of the liquid column within the tube willimpart some movement to the tube relative to an underlying surface orpassage along most of the 3 metre length of the tube, except for thosesections close to the drive mechanism or not supported by the underlyingsurface of passage.

As used herein, the terms “proximal” and “distal” are intended to haverelative positional meanings. Generally, the term “distal” is intendedto indicate a position or direction generally toward an end of the tubewhich is to be advanced within the tract ahead of the rest of the tube.The term “proximal” is intended to indicate a position or directiongenerally opposite to that of “distal” and may indicate a position ordirection toward an end of the tube to which the drive mechanism iscoupled. The described embodiments are generally concerned withadvancement of the probe in a distal direction.

Referring in particular to FIG. 1, a system 100 for advancing a probe160 is described in further detail. System 100 comprises advancementapparatus 110 responsive to a control module 115 to advance the probe160 within a tract 180 or other area when the probe 160 is placed withinthe tract 180 or other area.

Advancement apparatus 110 comprises a drive mechanism 130 coupled to aproximal end 142 of an elongate flexible tube 140. The tube has a distalend 144 at which the probe 160 is located. Drive mechanism 130 isresponsive to control signals received from control module 115 tooperate some form of drive means, such as a drive shaft that drives apiston, to cause reciprocating (back and forth) movement of a liquidcolumn 156 within the tube 140.

Flexible tube 140 defines a primary internal lumen 141 within whichliquid column 156 extends. This primary lumen 141 extends from adjacentdrive mechanism 130 to distal end 144 and the liquid column 156 extendssubstantially the full length of lumen 141. The liquid column 156 maynot extend right to the probe 160 in order to allow for a distal biasingmeans (described below) to be positioned proximally at probe 160 to biasliquid column 156 in a proximal direction once it has been distallyadvanced. Liquid column 156 comprises part of a liquid volume that isenclosed by tube 140, the distal biasing means and a fluid chamber ofthe drive mechanism 130. Examples of distal biasing means are shown anddescribed below in relation to FIGS. 21 to 36.

Elongate flexible tube 140 may have a diameter and length selected tosuit a particular exploratory application. The material of tube 140 maybe similarly selected to suit a particular application. For example,where advancement apparatus 110 is employed to advance a probe within abiological tract, such as a gastrointestinal tract, the tube may have amaximum external diameter of about 5 mm to about 15 mm (possibly closerto 7 mm) and may have a length of about 1 metre up to about 10 metres,possibly about 3 metres to about 6 metres. A tube length of about 3 to 4metres may be suitable for advancing probe 160 within an intestinaltract (i.e. into the small intestine) via the anus.

The material of the tube when used to explore an intestinal tract (i.e.for gastrointestinal endoscopy) may be formed of a suitable flexible andmedically inert material, such as suitable polyvinylchloride (PVC),silicone, latex or rubber materials. The material of tube 140 shouldallow tube 140 to be bendable to be able to be formed in a loop of arelatively small minimum diameter (depending on the application) withoutthe wall of the tube 140 kinking or collapsing or otherwise deforming todecrease the internal cross-sectional of the tube 140. For this purpose,the tube wall may be reinforced for increased structural integrity. Forendoscopy applications, the minimum loop diameter may be about 2 cm andmay range from about 1 cm to about 5 cm, for example.

For medical or veterinary applications in which it is desired to explorea vascular tract (i.e. for angioscopy), the tube diameter and length maybe commensurately smaller, for example about 3 mm to about 10 mm(possibly closer to 5 mm) in diameter and about 0.8 to about 3 m inlength, with probe 160 also being selected to have a suitably smalldiameter.

For exploration applications of a more industrial nature, such as forexploring pipes, ducts, containers, passages, tracts or other areas thatare inconvenient, unsafe or difficult for a person to access, tube 140may be formed of a more rugged material, at least on its externalsurface, to avoid or reduce damage to the tube as it passes alongpotentially abrasive surfaces. In some applications, the tube 140 needsto be relatively flexible and to be able to gain some purchase on asurface, structure or object across which the tube 140 is intended totravel. Thus, periodic perturbations formed along an external surface ofthe tube 140, as described in further detail below with reference toFIGS. 37A to 44, may assist in frictionally engaging the surface orstructure across which tube 140 is intended to travel.

System 100 may comprise a computer system 120 to provide control, signalprocessing and user interface functions in relation to advancement ofthe probe 160. Thus, computer system 120 may comprise control module115, which may be provided in the form of hardware, software or acombination of both. Although not shown, computer system 120 comprisesat least one processor and memory configured to perform the functionsdescribed herein.

Computer system 120 may comprise a user interface module 124. Computersystem 120 may also comprise a signal processing module 122 forreceiving and processing signals from probe 160, such as signalscorresponding to image data or status or feedback signals. Signalprocessing module 122 may interface with user interface module 124 inorder to provide images captured by probe 160 on a display (not shown)so that a user of system 100 may obtain visual feedback as probe 160progresses.

User interface module 124 may be configured to allow settings and/orfunctions of signal processing module 122 and control module 115 to bemodified or tailored to suit a particular environment, application orcircumstance.

Each of modules 115, 122 and 124 may be executable as program codestored in memory accessible to at least one processor and may besupplemented by suitable software and/or hardware components, such asinput-output components, operating system components, computerperipheral devices, etc.

Supplemental to drive mechanism 130, ancillary equipment 135 may beprovided under the control of control module 115 to provide power,signals and/or substances to probe 160. For example, ancillary equipment135 may provide electrical power to one or more light sources, such aslight emitting diodes (LED) positioned at a distal face of probe 160,for example, via at least one electrical conduit extending along tube140. Additionally, where probe 160 comprises an image-capturing devicehaving a charge-coupled device (CCD) or other suitably small imagingdevice, the at least one electrical conduit may also be used to powersuch an image-capturing device.

Ancillary equipment 135 may further comprise a source of purified airand/or water to be provided to probe 160 along one or more furtherconduits extending along tube 140. For this purpose, ancillary equipment135 may comprise a suitable compressor to pressurize the air, water orother substance to be provided to probe 160. Probe 160 may, depending onthe application, use an air vent positioned at its distal extremity toinsufflate a tract, such as a vascular or intestinal tract. The probe160 may also dispense water from an opening in its distal surface toclean an area in front of the imaging device, for example.

Ancillary equipment 135 may be partially or entirely under the controlof control module 115, which in turn may be controlled by a user via auser interface module 124, or it may be separately controlled, forexample by manual manipulation of suitable components of the ancillaryequipment, to provide the necessary interaction with probe 160.Depending on the application, ancillary equipment 135 may also comprisea mechanism for controlling capture of a material adjacent probe 160,for example to biopsy the material or otherwise subject it to lateranalysis. For this purpose, ancillary equipment 135 may mechanically,pneumatically and/or electrically communicate with probe 160 via afurther suction conduit and/or control cable conduit extending alongtube 140.

System 100 as shown in FIG. 1 may employ wireless data gathering ofimage data captured by the imaging device in probe 160, with such databeing received by a suitable antenna associated with computer system 120to provide the image data directly to data processing module 124 forprocessing. Alternatively or additionally, control signals may bewirelessly received from or transmitted to probe 160 responsive tocontrol module 115 and/or ancillary equipment 135 using a suitable shortrange low power radio transceiver.

In order to advance probe 160, drive mechanism 130 imparts a specificspeed profile to the liquid column 156 within lumen 141 in a repetitivemanner. An example of such a speed profile is depicted in the graph ofvelocity vs. time shown in FIG. 2. The movement of liquid column 156imparted by drive mechanism 130 may be divided into a forward movementsection 30 and a reverse movement section 34, with each such section 31,34 being divided into two parts or phases. The forward movement section30 is divided into a first phase 31, in which the drive mechanism 130imparts a gradual acceleration to a proximal end of the liquid column. Asecond phase 32 immediately following the first phase involves the drivemechanism 130 imparting a sharp deceleration up until the liquid column156 momentarily comes to rest at a rest position 33, which correspondsto the liquid 156 being moved to its distal-most position (correspondingto the point of maximum stroke) within tube 140. The reverse movementsection 34 may then comprise a first phase 35 of sharp acceleration inthe proximal direction, followed immediately by a second phase 36 ofgradual deceleration in the proximal direction, which continues untilthe liquid column 156 is again momentarily at rest at its proximal-mostposition, as indicated by reference numeral 37.

Although the first and second phases 31, 32, 35 and 36 of the forwardand rearward movement sections 30, 34, are shown in FIG. 2 as havingconstant change in velocity (i.e. constant acceleration) in each phase,such changes in velocity need not be linear. Rather, a velocity profileinvolving a sharp inversion (i.e. from a small but positive accelerationto a larger negative acceleration or vice versa) is considered to beeffective for imparting a transfer of momentum from the liquid column156 to the tube 140 in the forward (i.e. distal) direction.

If it is desired to retract the probe 160, the speed profile may beinverted to have a sharp acceleration and deceleration on either side ofthe proximal-most rest position indicated by reference numeral 37. Forexample, a sharp acceleration phase would be followed by a gradualdeceleration phase in the forward movement section and a gradualacceleration phase would be immediately followed by a sharp decelerationphase in the rearward movement section.

In some embodiments, the sharp velocity inversion may be employed inonly the forward movement section 30 or only the reverse movementsection 34, with the other movement section having relatively gradualchanges in velocity.

Although the drive mechanism can be operated to impart a desired speedprofile to a proximal end of the liquid column 156, because movement ofthe liquid column 156 relies on pressure differences created by thedrive mechanism and communicated to the liquid column 156 for theproximal end 142 to the distal end 144, there may be some pressure lossover the length of the liquid column 156. Thus the speed profileimparted by the drive mechanism 130 to the liquid column 156 at theproximal end 142 may not be the same speed profile as is experienced bythe liquid column 156 at the distal end 144. In order to minimize orreduce the loss of pressure across the length of tube 140, the generallycylindrical wall of tube 140 may be reinforced to resist expansion orcollapsing of the tube wall in response to pressure differences inducedalong the liquid column 156. Additionally, an internal diameter of lumen141 may be gradually reduced over the length of tube 140 from a firstinternal diameter at the proximal end 142 to a lesser second internaldiameter at the distal end 144. This reduction in diameter may beachieved in a smooth or stepped manner. For example, stepped reductionsmay comprise reductions of, say 0.05 mm or 0.1 mm every 15, 20, 25 or 30cm along the tube 140. This diametrical reduction may be linear ornon-linear along the length of tube 140. In this context, the reductionin internal diameter along the length of tube 140 is independent of anyperiodic variation in internal lumen diameter due to periodicperturbations, such as are described below in relation to FIGS. 37A to44.

Pressure loss along tube 140 may be minimized by using a liquid that hasa density at room temperature and at internal body temperatures aboutthe same as or greater than that of water at such temperatures. Liquidsof such densities generally do not appreciably compress under therelatively small pressure exerted by drive mechanism 130. Thus, water,such as purified or demineralised water for example, may be used as theliquid of liquid column 156.

In use of the system 100, most of the length of tube 140 may be coiled,curled or held slack so that it can straighten gradually as the distalend 144 and probe 160 are positioned in and advance within the tract 180or other area. Thus, as probe 160 advances under the operation of drivemechanism 130, more and more of tube 140 will be received within thetract 180. Once all of the slack in tube 140 is taken up and that partof tube 140 that is outside of the tract 180 cannot advance any further,probe 160 will have reached the limit to which it can extend within thetract 180.

Once the endoscopy, angioscopy or other form of exploration iscompleted, probe 160 can be withdrawn from the tract 180 by gentlymanually pulling on that part of tube 140 which remains outside of tract180. This may be assisted and/or substituted by operating drivemechanism 130 to provide an inverted speed profile to liquid column 156tending to impart a reverse motion and retract tube 140 in a generallyproximal direction.

Advancement apparatus 110 is shown and described in further detail inrelation to FIGS. 3, 4A and 4B. As shown in FIG. 3, advancementapparatus 110 comprises drive mechanism 130 coupled to proximal end 142of tube 140. Probe 160 is coupled to distal end 144 of tube 140. Drivemechanism 130 may comprise a drive piston 352 that is movable in areciprocating manner in relation to a chamber 351 defined by a chamberwall 350. Movement of piston 352 within wall 350 can pressurize anddepressurize liquid, such as water, within chamber 351, either forcingliquid out of chamber 351 through an opening 356 or drawing it back intochamber 351. Various alternative embodiments of drive mechanism 130 areshown and described below in relation to FIGS. 16A to 20.

Drive mechanism 130 may comprise a drive wheel 322 mounted to contactand act upon a drive member 324 coupled to a drive shaft 354 whichdrives piston 352. Drive wheel 322 and drive member 324 are arranged sothat rotation of drive wheel 322 in a clockwise or anticlockwisedirection causes linear movement of drive member 324 in a proximal ordistal direction, respectively. Drive wheel 322 may be securelypositioned within a mounting bracket 310 for mounting to a surfaceand/or structure (not shown) via one or more fasteners received throughslots 312 formed in mounting bracket 310. Drive member 324 rests on asupport 326 fixedly coupled to mounting bracket 310. Drive member 324 isslidable relative to support 326 with relatively little friction.

In some embodiments, drive member 324 and/or drive shaft 354 may beremovably attached to piston 352 so that chamber 350 and all partsdistal thereof (including tube 140 and probe 160) can be replaced afterone or more uses or due to performance deterioration.

Drive wheel 322 may be rotated under the control of a stepper motor (notshown) comprised in drive mechanism 130. Control of the stepper motormay be performed by control module 115 using a suitable driver programsuch as is commonly available with commercially available steppermotors. Control module 115 may be configured to cause the stepper motorto rotate drive wheel 322 so as to impart the desired speed profile tothe proximal end of liquid column 156 by advancement and retraction ofpiston 352 within wall 350.

As shown in FIGS. 3 and 4A, advancement mechanism 110 may comprise aY-type junction 330 coupled between outlet 356 of drive chamber 351 andone end of tube 140. The Y-type junction 330 acts as a means forallowing one or more conduits 340, 342 to pass or be merged into aproximal part of tube 140 so that such conduits extend within lumen 141and are coextensive with liquid column 156 along most of the length oftube 140. Y-type junction 330 has a proximal end 332 coupled for fluidcommunication with drive chamber 351 via opening 356. Proximal end 332forms a first limb of Y-type junction 330, while a second limb 334extends at an acute angle away from proximal end 332 as shown in FIG. 3.Y-type junction 330 has a distal end 336 through which passes the liquidcolumn 156 and the fluid conduits 340, 342.

Conduit 340 may define a secondary lumen through which other conduitspass in order to communicate signals and/or substances between ancillaryequipment 135 and probe 160. Such conduits may include, for example, airand/or water passages, electrical conduits for signal transmission,control cables, a biopsy tube, etc. Conduit 342 may comprise electricalconduits, for example to provide a voltage to one or more light sourcesexposed at a distal face 162 of probe 160. Conduit 342 may be bonded toconduit 340 so as to extend in a spiral therealong as both conduits 340and 342 extend within lumen 141 of tube 140. Liquid column 156 extendswithin lumen 141 in the spaces 376 not taken up by conduits 340, 342.

As shown in FIGS. 4A and 4B, hollow fluid connectors 410, 412, 414 and416 may be used to couple different sections of advancement apparatus110 together. For example, a first connector 410 couples proximal end332 of Y-type junction 330 to a tube 440 that is coupled to wall 350around opening 356. A second connector 412 couples a distal end 336 ofY-type junction 330 to a proximal end 142 of tube 140. A third connectorcouples a distal end of tube 140 to a distal tube section 450 which inturn is coupled to a flexible section 460 via a fourth connector 416.Flexible section 460 may be directly coupled to probe 160 and may bedirectionally controlled, for example by use of control cables extendingwithin the conduits 340 and/or 342.

Distal end section 450 includes a membrane 454 sealing a distal end ofliquid column 156 by sealing against an inner wall of distal tubesection 452 and sealing against outer walls of conduits 340, 342. Agenerally cylindrical sealing section 455 may also be provided toprevent fluid from liquid column 156 entering into flexible section 460.

Flexible section 460 may define an internal lumen or plenum 464 throughwhich conduits 340, 342 pass to be coupled to probe 160. Flexiblesection 460 has a flexible wall 462 defining the plenum 464. Flexiblewall 462 is coupled to fourth connector 416 at a proximal end offlexible wall 462 and to the probe 160 at a distal end of flexible wall462.

As shown in FIG. 4B, probe 160 may house an imaging device 474 and oneor more light sources 472, such as LEDS, positioned at the distal face162 in order to shine light distally and capture images of the areailluminated by light sources 472.

Referring now to FIGS. 5A and 5B, an alternative form of distal endsection 450 is shown and described. Alternative distal end section 550is shown schematically in FIGS. 5A and 5B and is not to scale. Distalend section 550 comprises a flexible membrane 554 sealingly coupled toan inner surface of cylindrical wall 552 and extending inwardly in acone shape in a distal direction to be coupled circumferentially andsealingly around conduit 340. Flexible membrane 554 is positioned sothat liquid column 156 is disposed generally proximally of flexiblemembrane 554, with a second fluid volume 556, such as air, beingdisposed distally of flexible 554. Second fluid volume 556 should be acompressible fluid volume so that, when liquid column 156 is moveddistally due to the action of drive mechanism 130, flexible membrane 554can deform, as shown in FIG. 5B, and compress second fluid volume 556somewhat. This compression of second fluid volume 556 and elasticdeformation of flexible membrane 554 provides a biasing function becausethe deformation and compression tend to push back on liquid column 156in a proximal direction following distal movement of liquid 156.

Referring now to FIG. 6, an alternative schematic representation ofsystem 100 is provided. System 100 as depicted in FIG. 6 has similarfeatures and functions to those described above in relation to FIG. 1.In addition, computer system 120 comprises a display 612 for displayingcaptured images, an input device 614, such as a keyboard, and a usercontrol device 616, such as a joy stick, for interfacing with controlmodule 115. Ancillary equipment 135, which may be integrated with acomputer system 120, is used to provide air and/or water and/or suctionfor a biopsy tube, if appropriate. Control module 115 may be configuredto translate input from user input control device 616 into controlsignals to be provided to a directionally controllable flexible section662 coupled intermediate probe 160 and a distal end section (such as isshown and described in relation to FIG. 4B, 5A, 5B or 21 to 36) in orderto change the position of probe 160.

Conduits 340, 342 are provided within tube 140 to provide suitablecontrol and/or feedback functions to flexible section 662 and probe 160.Alternatively or in addition, other conduits or control means may beprovided to directionally control probe 160. As shown in FIG. 6, distalend section 450 (or 550, 2150, 2250, 2350, 2450, 2550, 2750, 2950, 3050,3150, 3250, 3450 or 3650), flexible section 662 and probe 160 form adistal portion 644 at a distal end of tube 140. Versions of system 100shown in FIG. 6 may be suited for endoscopy or angioscopy, for example.

Referring now to FIGS. 7A and 7B, a tube 740 according to some specificembodiments of tube 140 is shown and described. Tube 740 has a generallycylindrical wall 750 defining a lumen 741 through which liquid column156 and optionally conduits 340, 342 extend. Longitudinal reinforcingmembers 752 may be embedded or otherwise disposed within wall 750,spaced circumferentially around wall 750. Alternatively or in addition,reinforcing members 752 may comprise conduits for coupling to probe 160to provide the conduit functions described above.

Referring now to FIGS. 8A and 8B, a tube 840 according to some specificembodiments of tube 140 is shown and described. Tube 840 has asubstantially cylindrical wall 850 defining a lumen 841 and has aplurality of reinforcing members 852 disposed circumferentially aroundthe outside of wall 850. Reinforcing members 852 may be adhered orotherwise bonded to an external surface of wall 850 in a suitablyflexible manner to resist changes in diameter of wall 850, whileallowing tube 840 to curve as necessary while passing along a tract.Reinforcing members 852 are thus similar in function and purpose toreinforcing members 752 of tube 740.

Tubes 940, 1040 and 1140, as shown in FIGS. 9A, 9B, 10A, 10B, 11A and11B, also use respective reinforcing members 952, 1052 and 1152 in orderto provide structural integrity to the wall of the tube to resistcollapsing or expansion of the tube wall due to pressure changes, whileallowing adequate flexion to allow flexible passage through a convolutedtract. FIGS. 9A and 9B show the reinforcing members 952 formed in aspiral around and along an outside of wall 950 that defines a centrallumen 941.

Tube 1040 is similar to tubes 840 and 940, in that tube 1040 combineslongitudinal and spiral reinforcing members 1052, thus combining thefeatures of tubes 840 and 940. Reinforcing members 1052 are disposedaround the outside of wall 1050 which defines a central lumen 1041.

Tube 1140 is similar to tube 940 except that reinforcing members 1152are formed in separate spirals that cross each other as they travelaround wall 1150. Reinforcing members 1152 are therefore oppositelyangled with respect to their spiral forms. Such spiral forms may havedifferent angles relative to the longitudinal axis of tube 1140 and maytherefore have differently spaced coils. Wall 1150 defines a centrallumen 1141 which, like lumens 741, 841, 941 and 1041, allows passage ofliquid column 156 therewithin.

In some embodiments, reinforcing members 752, 852, 952, 1052 and 1152may comprise one or more conduits for coupling to probe 160 to providethe conduit functions described above. Thus, such reinforcing membersmay provide a dual function. For reinforcing members 852, 952, 1052 and1152 disposed around the outside of the tube wall, such members may bebonded to the outside of the wall, for example by a suitable adhesive orultrasonic welding or by overlay of an adhesive layer or coating. Formedical applications, such adhesive or bonding materials should besuitably medically inert. In some embodiments, reinforcing members 952,1052 and 1152 may act as periodic perturbations along the exterior ofthe tube wall for increasing frictional engagement of the tube with asurrounding area to a degree sufficient to enhance the ability of thetube to progress within the tract or other area under the action ofdrive mechanism 130.

FIGS. 12A, 12B, 13A, 13B, 13C, 14A, 14B, 15A and 15B illustrate variousspecific embodiments of tube 140 with respect to the arrangement ofconduits extending within the lumen 141 of tube 140. As shown in FIGS.12A and 12B, a tube 1240 may have multiple conduits 1262 extendingwithin a lumen 1241 defined by tube 1250. Conduits 1262 may extend in anarrangement involving multiple conduits 1262 spiraling around a centralconduit 1262, which may be larger in diameter (e.g. to house furtherconduits) than the spiraling conduits 1262. Conduits 1262 may take upmost of the space within lumen 1241, while leaving sufficient space forliquid column 156 to be movable within the remaining spaces 376.

As shown in FIGS. 13A, 13B and 13C, tube 1340 has a generallycylindrical outer wall 1350 defining at least one lumen 1341. At leastone dividing membrane 1364 extends within lumen 1341 to divide theinternal cross-sectional area defined by wall 1350 into two or moresections, such as are illustrated in FIGS. 13B and 13C. FIG. 13Billustrates a tube 1340 a in which a dividing membrane 1364 divideslumen 1341 into a section along which conduits 1362 pass and anotherportion along which liquid column 156 is free to pass. FIG. 13Cillustrates an alternative cross-section of FIG. 13A, where a tube 1340b has at least two dividing membranes 1364 which divide lumen 1341 intofour sections, two of which are used to house conduit 1362, while theremaining two portions of lumen 1341 allow free movement of liquidcolumn 156 therealong.

As shown in FIGS. 14A and 14B, a tube 1440 according to some embodimentshas a wall 1450 defining a lumen 1441 that is a primary lumen withinwhich passes a secondary conduit 1464 defining a secondary lumen. Thissecondary conduit 1464 houses a plurality of conduits 1462, containedwithin the generally cylindrical form of the secondary lumen. Thesecondary conduit 1464 may be adhered or otherwise bonded to orintegrally formed with an internal surface of wall 1450.

Referring now to FIGS. 15A and 15B, a tube 1540 according to furtherembodiments is shown, having a wall 1550 defining a lumen 1541. Lumen1541 is a primary lumen through which extends a secondary conduit 1564defining a secondary lumen similar to secondary conduit 1464, exceptthat it is positioned centrally within primary lumen 1541. Secondaryconduit 1564 houses a plurality of conduits 1562 within a generallycylindrical tube. Secondary conduit 1564 may comprise a tube that ispositioned centrally within primary lumen 1541 by means of a series ofspaced positioning elements, such as locating ribs, extending inwardlyfrom wall 1550 in a manner that does not appreciably obstruct movementof liquid column 156 within primary lumen 1541.

Referring now to FIGS. 16A, 16B, 17A, 17B, 18, 19 and 20, variousembodiments of drive mechanism 130 are illustrated schematically. Asshown in FIGS. 16A and 16B, drive mechanism 130 may comprise a simplepiston 1652 and drive shaft 1654 arranged to move piston 1652 back andforth within a chamber 1651 defined by a wall 1650. As piston 1652repeatedly moves back and forth within wall 1650, liquid in chamber 1651is repeatedly forced out of an opening 1656 formed in wall 1650 and thendrawn back into chamber 1651 through opening 1656. Piston 1652 sealinglyengages wall 1650 so that liquid in chamber 1651 does not passproximally of piston 1652.

The drive mechanism arrangement depicted in FIGS. 17A and 17B issubstantially similar to that shown in FIGS. 16A and 16B, except that alongitudinally compressible/extensible bellows or sylphon 1770 isarranged to extend between a distal part of wall 1650 and piston 1652,thereby defining a fluid volume 1751 bounded by the piston 1652 at oneend, the accordion-like walls of sylphon 1770 and the walls 1650 thatdefine the distal opening 1656. Sylphon 1770 obviates the need forsealing engagement of piston 1652 with wall 1650, for example where suchengagement might entail an undesirable amount of friction or may bedifficult to seal properly. In some embodiments, sylphon 1770 may besubstituted by another flexible membrane that is also flexiblycompressible but that is less structured than sylphon 1770.

Referring now to FIG. 18, further embodiments of drive mechanism 130 aredescribed, which employ an elastically deformable flexible membrane 1870forming one wall of a housing enclosing a liquid volume 1851. A housingwall 1850 cooperates with flexible membrane 1870 to enclose liquidvolume 1851. A drive shaft 1854 coupled to a flat or somewhat curvedpiston 1852 is used to push inwardly on flexible membrane 1870 tothereby expel liquid from liquid volume 1851 out of an opening 1856 inthe wall 1850 of the housing. Upon release (i.e. retraction) of thedrive shaft 1854, flexible membrane 1870 is allowed to at leastpartially return to a position from which it is resiliently deflected,thereby increasing the amount of liquid in liquid volume 1851 bycreating suction and thereby drawing liquid back through opening 1856.Drive shaft 1854 is operated by the drive mechanism to repeatedlydeflect flexible membrane 1870 to move liquid column 156 back and forthwithin lumen 141. In some embodiments, drive shaft 1854 may be coupledto flexible membrane 1870 so that retraction of the drive shaft 1854causes the flexible membrane 1870 to more strongly return to its relaxedposition (or at least a less deflected position), thereby creatinggreater suction than may be achievable due to the flexible membrane 1870alone.

The drive mechanism schematically illustrated in FIG. 19 operates on asimilar principle to the drive mechanism illustrated in FIG. 18, exceptthat instead of a pushing rod and piston, a cylindrical piston iseccentrically rotated about a drive shaft 1954 to cyclically inwardlydeflect a resilient flexible membrane 1970, thereby decreasing thevolume of liquid 1951 within a housing defined by wall 1950 and flexiblemembrane 1970. As piston 1952 rotates around drive shaft 1954, liquid ispushed outward and sucked inward through opening 1956 formed in wall1950. In some embodiments, piston 1952 may have an oblong, noncircular(but curved) shape to impart a specific speed profile to liquid column156. For example, piston 1952 may be more bulb-shaped or have arelatively flat face, rather than circular, but still rotateeccentrically around drive shaft 1954.

Referring now to FIG. 20, a further alternative drive mechanism is shownthat uses electromagnetic elements 2054 positioned outside a wall 2050that defines a chamber 2051. A piston 2052 is movable under the controlof electromagnetic elements 2054 so as to push liquid out of chamber2051 through opening 2056 formed in wall 2050 and to subsequently suckliquid back into chamber 2051. Piston 2052 is formed of a suitablematerial to enable electromagnetic control using elements 2054 and, likethe drive mechanism of embodiments described above in relation to FIGS.16A, 16B, 17A and 17B, either uses a sealing engagement of piston 2052with wall 2050 or a sylphon to obviate such sealing engagement.

The drive mechanism embodiments described above in relation to FIGS. 16Ato 20 provide only some examples of possible mechanisms for creatingreciprocating movement of liquid column 156 within tube 140. Furtherembodiments may be employed, for example involving pneumatic, hydraulic,electrical or mechanical means to create repeated positive and negativepressure differences within and along liquid column 156, tending tocause reciprocating movement thereof in a manner that is suitablycontrollable to impart a desired speed profile to liquid column 156.

Referring now to FIGS. 21 to 36, various embodiments of a distal biasingsection are shown and described. Similar to distal biasing section 550,these embodiments use various different means or mechanisms to bias theliquid column 156 back in the proximal direction once it has beenadvanced distally. This may also assist in avoiding collapse of the tubewall as the liquid column is sucked proximally under the negativepressure by drive mechanism 130. Accordingly, the distal biasingsections shown in FIGS. 21 to 36 are all intended to be positioneddistally of the liquid column 156, but proximally of probe 160 and theyare intended to be positioned within a tube wall, either provided bytube 140 or a tube section adjacent or contiguous with tube 140.

Distal biasing chamber 2150 shown in FIG. 21 has the most basicconstruction, consisting mainly of a cylindrical wall 2152 with amovable element 2154, such as a piston, movable within a chamber 2156.At its proximal face, element 2154 is exposed to the distal end ofliquid column 156 and, in response to distal movement of liquid column156 is pushed distally. Chamber 2156 comprises a compressive fluidvolume, such as air, and is enclosed by wall 2152 and a distal endprovided by another distally positioned structure (not shown). Element2154 sealingly engages wall 2152 so that liquid from liquid column 156does not pass into chamber 2156. The pressure increase in chamber 2156as a result of distal movement of element 2154 provides a proximallydirected force on element 2154 to return it in the proximal direction asliquid column 156 is sucked proximally by the action of drive mechanism130.

The distal biasing chamber 2250 of FIG. 22 operates in an identicalmanner to that of FIG. 21, except that wall 2252 defines more restrictedend passages at the proximal and distal ends. Movable member 2254 moveswithin wall 2252 to compress chamber 2256 in response to distal movementof liquid column 156.

Distal biasing chamber 2350 shown in FIG. 23 operates identically tothat shown in FIG. 21, except that it has a distal end wall 2380 that,together with movable element 2350 at wall 2352, defines an enclosedchamber 2356 comprising a compressible fluid, such as air.

Distal biasing chamber 2450 shown in FIG. 24 is similar to that of FIG.23, except that a flexible membrane 2480 is provided as the distal endwall. Together with movable element 2454 and wall 2452, flexiblemembrane 2480 defines an enclosed chamber 2456 comprising a compressiblefluid, such as air. Flexible membrane 2480 expands and contracts,depending on the pressure within chamber 2456 and may assist in biasingmovable element 2454 in the proximal direction.

Distal biasing chamber 2550 shown in FIGS. 25 and 26 are similar to thatshown in FIG. 22, except that movable element 2554 is biased distally bya spring 2580 housed within wall 2552. Spring 2580 compresses whenmovable element 2554 progresses distally and therefore tends to biasmovable element 2554 in the proximal direction. Spring 2580 sits withina chamber 2556 defined distally of movable element 2554.

Distal biasing chamber 2750 shown in FIGS. 27 and 28 is identical tothat shown in FIGS. 25 and 26, except that instead of a spring, aresiliently deflectable mesh or sponge 2780 is provided within a chamber2756 defined by wall 2752 distally of movable element 2754,

Distal biasing chamber 2950 shown in FIG. 29 is similar to thosedescribed above, but has a sylphon 2970 coupled to a proximal side ofmovable element 2954 to define a proximal chamber 2958 that isexpandable in response to distal movement of liquid column 156, but thattends to retract according to the shape memory of the sylphon and/orincreased pressure in distal fluid volume 2956, thereby biasing themovable element 2954 in the proximal direction. Sylphon 2970 is coupledat the proximal end of distal biasing chamber 2950 to a wall 2952.Compressive distal fluid volume 2956 is provided distally of movableelement 2954 to further bias movable element 2954 in the proximaldirection.

Distal biasing chamber 3050 shown in FIG. 30 employs a first sylphon3070 in a similar manner to that shown in FIG. 29 and a second sylphon3071 disposed within a distal chamber 3056 defined by wall 3052. Theopposite shape memories of first and 20 second sylphons 3070 and 3071tend to bias movable element 3054 in the proximal direction. Distalbiasing chamber 3150 shown in FIG. 31 is identical to that shown in FIG.30, except that its distal end wall is substituted by a resilientlydeflectable flexible membrane 3180.

Distal biasing chamber 3250 shown in FIGS. 32 and 33 represents acombination of the spring and sylphon features shown and described inrelation to FIGS. 25, 26 and 29. Distal biasing chamber 3450 shown inFIGS. 34 and 35 represents a combination of the sylphon and sponge/meshfeatures and functions described above in relation to FIGS. 27, 28 and29. All of FIGS. 32 to 35 employ a proximally disposed sylphon 3270/3470defining a proximal chamber 3258/3458 and coupled to a movable element3254/3454, with a biasing element, such as a spring 3280 or sponge ormesh 3480 positioned distally of the movable element 3254/3454 withinwall 3252/3452.

Distal biasing chamber 3650 shown in FIG. 36 has a wall 3652 thatdefines an internal compressible fluid chamber 3656 between aresiliently deflectable proximal flexible membrane 3654 and aresiliently deflectable distal flexible membrane 3680. Both of theflexible membranes 3654 and 3680 may deflect distally in response todistal movement of the liquid column 156 and will tend to return to arest position in which they are not distally displaced, thereby tendingto bias liquid column 156 in the proximal direction.

Referring to FIGS. 37A, 37B, 38A, 38B, 39A and 39B, various embodimentsof tube 140 are described. Each of the embodiments has a nominal wallthickness X relative to which periodic perturbations are formed along anexternal surface of the tube. The periodic perturbations have a maximumamplitude Y and a separation Z. As shown in these Figures, the periodicperturbations are formed to have a pattern generally resembling afir-tree or the serrations on a saw blade. However, in some embodimentsthe periodic perturbations may be more rounded and/or not proximallyswept (as in the case of the fir-tree pattern).

As shown in FIG. 37A, the minimum thickness of the wall of tube 3740 isX with the thickness of the wall varying along the periodicperturbations between X and X+Y. Tube 3745 shown in FIG. 37B has a wallthickness varying between the nominal thickness X and X−Y.

FIGS. 38A and 38B show a slightly different fir-tree pattern than FIGS.37A and 37B, without an undercut, but are otherwise substantially thesame, with tube 3845 having a larger nominal thickness X than tube 3840.

Tube 3940 shown in FIG. 39A has a greater spacing Z between the periodicperturbations, with the thickness of the wall varying between thenominal thickness X and X+Y. Tube 3945 shown in FIG. 39B is the same asFIG. 39A, but with a larger nominal thickness X and the wall thicknessvarying between X and X−Y.

In the described and depicted embodiments, the separations of theperiodic perturbations may be anywhere between say about 2 mm and about50 mm. The variation in thickness (i.e. amplitude) Y may be in the orderof 0.5 mm to about 5 mm, depending on the exploration application forwhich the tube is to be used. The nominal wall thickness X may be about0.5 mm to about 10 mm, depending again on the application. In someembodiments, variation of the wall thickness may be based on proportionsof amplitude Y (or M, described below), for example the thickness mayvary between X+½Y and X−½Y or between X+⅓Y and X−⅔Y.

Referring now to FIGS. 40A, 40B, 41A, 41B, 42A and 42B, variousembodiments of tube 140 are depicted and described in which periodicperturbations are provided on an internal wall of the tube. The nominalthickness L of the tube wall may vary, together with the amplitude M andperiod N of the periodic perturbations. The various embodiments depictedhave a generally proximally swept fir-tree pattern, which may also bedescribed as a saw-tooth pattern, although rounded and/ornon-proximally-swept perturbations may also be employed. Tube 4040 isshown in FIG. 40A with the wall thickness varying between the nominalthickness L and L+M. In FIG. 40B, tube 4045 has a nominal wall thicknessvarying between L and L−M. The tubes 4140 and 4145 shown in FIGS. 41Aand 41B are substantially the same as tubes 4040 and 4045, except forthe sharper undercut of the fir-tree pattern shown in the latterfigures. Tube 4240 shown in FIG. 42A has a nominal wall thickness L thatvaries between L and L+M. Tube 4245 has a nominal thickness L thatvaries between L and L−M, as shown in FIG. 42B. In some embodiments,variation of the wall thickness may be based on proportions of amplitudeM, as described above.

As shown in FIGS. 43A and 43B, embodiments of tube 140 include tubes4340 and 4345, representing combinations of tube embodiments 38A, 38B,41A and 41B, described above. Tube 4340 has a nominal thickness X, withthe thickness varying between X and X+Y+M. The spacing Z of the externalperiodic perturbations may be different from the spacing N of theinternal periodic perturbations. Additionally, the internal and externalperiodic perturbations need not have the same saw-toothed or fir-treeshape. Specifically, one of the internal or external periodicperturbations may be saw-toothed, while the other may be more roundedand more spaced apart. Tube 4345 shown in FIG. 43B is similar to tube4340, except that it has a greater nominal thickness X, with thethickness varying between X and X−Y−M. In some embodiments, variation ofthe wall thickness may be based on proportions of amplitude M and/or Y,as described above.

FIG. 44 shows a schematic representation of a tube 4440 according tosome embodiments in which a first section 4441 of the tube may haveinternal periodic perturbations, while a second section of the tube 4440may have external periodic perturbations. The first and second sectionsof the tube may be separated by a section 4442 that does not contain anyinternal or external periodic perturbations.

According to the described embodiments, some embodiments of tube 140 mayinvolve periodic perturbations along part or a substantial portion of aninternal or external surface of the wall of tube 140. Such periodicperturbations on the internal surface of the tube wall can assist inproviding greater resistance to advancement of liquid column 156,because of the proximally swept shape of the perturbations in someembodiments, thereby improving momentum transfer from liquid column 156to tube 140 in the distal direction. The periodic perturbations formedon the external wall of tube 140 may similarly assist in advancing thetube 140 by providing a greater resistance to movement of tube 140 inthe proximal direction than in the distal direction so that retractionof liquid column 156 results in a small tube movement in the rearwarddirection compared with the tube movement achieved in the forwarddirection.

The different embodiments of tube 140 described herein may be combined,for example so as to provide periodic perturbations in combination withreinforcing members such as those extending externally along the tubewall or within the tube wall. In particular, the extension of conduits,such as conduits 340, 342, within lumen 141 can be combined withinternal and/or external periodic perturbations in the tube wall and/ormay be combined with external or embedded longitudinal or spiralreinforcing members.

Described embodiments of tube 140 may be formed by a moulding process,for example, using suitable materials as described above.

The embodiments described herein and illustrated in the drawings areintended to be provided by way of example and without limitation.Accordingly, the described embodiments are intended to be non-limitingand should be interpreted accordingly.

1. Apparatus comprising: an elongate flexible tube sized to be receivedwithin a tract and having a proximal end and a distal end; a drivemechanism coupled to the proximal end of the tube; and a liquid columnextending from the proximal end to the distal end; wherein the drivemechanism is configured to cause movement of the liquid column withinthe tube to impart forward momentum to the tube and thereby promoteadvancement of at least the distal end of the tube within the tract whenat least the distal end is received within a part of the tract. 2-42.(canceled)